Boot loader for active cable assemblies

ABSTRACT

According to one embodiment, an active cable assembly may include a cable end, a data receiver, a controller characteristic circuit, and a controller. The data receiver, operable to receive a DC-balanced data signal, can be electrically coupled to a conductive input data line of the cable end. The controller characteristic circuit can be electrically coupled to the conductive input data line. The controller can be communicatively coupled to the data receiver. The controller may include a configurable communication port electrically coupled to the controller characteristic circuit, and memory for storing a boot loader. The controller can execute the boot loader to set the configurable communication port as an output for controller data signals and as an input for the controller data signals.

PRIORITY APPLICATION

This application is a continuation of International Application No.PCT/US14/68690, filed on Dec. 5, 2014, which claims the benefit ofpriority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.61/914,576, filed on Dec. 11, 2013, the content of which is relied uponand incorporated herein by reference in its entirety.

BACKGROUND

Field

The present disclosure generally relates to apparatuses, and methods forfacilitating debugging and reprogramming of active cable assemblies.

Technical Background

Active cables can be an attractive alternative to passive cables,especially as data rates increase. Active cables can utilizemicroprocessors and signal processing circuitry to improve datatransmission performance compared to passive data cables. Active cablescan be manufactured in high volumes and can be amenable to manufacturingin low-cost manufacturing centers. However, the low-cost centers can beisolated from the development team spatially and temporally. Suchisolation can negatively impact yield and flow down of designimprovements as changes are made to the product during development orover the product life cycle.

Accordingly, alternative active cable assemblies, as well asapparatuses, systems and methods for facilitating debugging andreprogramming of active cable assemblies, are desired.

SUMMARY

Embodiments of the present disclosure relate to active cable assembliesand, more specifically, active cable assemblies configured to enablecommunication between two or more electronic devices using acommunications standard. Generally, the embodiments described hereinenable fiber optic cable assemblies utilized in conjunction with, forinstance, the USB 3.0 protocol to be reprogrammed and debugged via acommunication link established with a controller of the active cableassembly. Embodiments also relate to methods and systems forfacilitating communication with the controller of an active cableassembly.

According to one embodiment, an active cable assembly may include acable end, a data receiver, a controller characteristic circuit, and acontroller. The cable end may include a conductive input data line. Thedata receiver can be electrically coupled to the conductive input dataline. The data receiver can be operable to receive a DC-balanced datasignal. The controller characteristic circuit can be electricallycoupled to the conductive input data line. The controller can becommunicatively coupled to the data receiver. The controller may includea configurable communication port electrically coupled to the controllercharacteristic circuit, and memory for storing a boot loader. Thecontroller can execute the boot loader to set the configurablecommunication port as an output for controller data signals. The bootloader can be executed to set the configurable communication port as aninput for the controller data signals. The input can have a relativelyhigh controller input impedance. The output can have a relatively lowcontroller impedance with the relatively low controller impedance beinglower than the relatively high controller input impedance

According to another embodiment, a method of communicating with acontroller of an active cable assembly may include setting a firstconfigurable communication port and a second configurable communicationport to outputs. The first configurable communication port can becommunicatively coupled to a first input data line. The secondconfigurable communication port can be communicatively coupled to asecond input data line. The first input data line can be driven with thefirst configurable communication port and the second input data line canbe driven with the second configurable communication port to a voltageof about 0 volts for a discharge time period. The first configurablecommunication port and the second configurable communication port can beset to inputs. A voltage can be detected automatically with thecontroller at the first configurable communication port, the secondconfigurable communication port, or both. When the voltage is greaterthan a threshold voltage, the first configurable communication port canbe set to an input, and the second configurable communication port canbe set to an output. A controller data signal can be communicated fromthe second configurable communication port to the second input dataline.

According to yet another embodiment, an active cable assembly mayinclude a data receiver, a first isolation capacitor, a second isolationcapacitor, a first input data line, a second input data line, a firstisolation resistor, a second isolation resistor, and a controller. Thedata receiver can be operable to receive a DC-balanced data signal. Thefirst isolation capacitor can be electrically coupled to the datareceiver. The second isolation capacitor can be electrically coupled tothe data receiver. The first input data line can be electrically coupledto the first isolation capacitor. The first isolation capacitor can bedisposed in series between the first input data line and the datareceiver. The second input data line can be electrically coupled to thesecond isolation capacitor. The second isolation capacitor can bedisposed in series between the second input data line and the datareceiver. The first isolation resistor can be electrically coupled tothe first input data line and the first isolation capacitor. The secondisolation resistor can be electrically coupled to the second input dataline and the second isolation capacitor. The controller may include afirst configurable communication port and a second configurablecommunication port. Each of the first configurable communication portand the second configurable communication port can be set to an inputand an output for controller data signals. The first configurablecommunication port can be electrically coupled to the first isolationresistor. The second configurable communication port can be electricallycoupled to the second isolation resistor.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments, andtogether with the description serve to explain principles and operationof the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The components of the following figures are illustrated to emphasize thegeneral principles of the present disclosure and are not necessarilydrawn to scale. The embodiments set forth in the drawings areillustrative and exemplary in nature and not intended to limit thesubject matter defined by the claims. The following detailed descriptionof the illustrative embodiments can be understood when read inconjunction with the following drawings, where like structure isindicated with like reference numerals and in which:

FIG. 1 schematically depicts one end of an active cable assemblyaccording to one or more embodiments described and illustrated herein;

FIGS. 2A-2C schematically depict various communication modes ofconfigurable communication ports of the active cable assembly depictedin FIG. 1 according to one or more embodiments described and illustratedherein;

FIG. 3 schematically depicts a system having an active optical cableassembly coupled to a host device according to one or more embodimentsdescribed and illustrated herein;

FIG. 4 schematically depicts the system of FIG. 3 comprising anisolation scheme for a communication circuit of an active opticalassembly according to one or more embodiments described and illustratedherein;

FIG. 5 schematically depicts a system having an active optical cableassembly coupled to a programming fixture according to one or moreembodiments described and illustrated herein; and

FIG. 6 schematically depicts the system of FIG. 5 comprising anisolation scheme for a communication circuit of an active opticalassembly according to one or more embodiments described and illustratedherein.

DETAILED DESCRIPTION

Some aspects of the present disclosure are directed to communicationwith a controller of an active cable assembly to debug or reprogram theactive cable assembly. It is noted that some active cable standards(e.g., Thunderbolt) have dedicated data lines for communication with themicroprocessor, while other communication standards (e.g. USB 3.0) maymake no provision for microprocessors, data lines for communication withmicroprocessors, or both. Embodiments of the active cable assembliesdescribed herein can be utilized to retrofit microprocessorcommunication into the limited data lines of an application that makesno provision for microprocessor communication. In some embodiments, thehigh-speed AC-coupled data lines can be overloaded with a low-speedDC-coupled communication circuit. Although embodiments may be describedwithin the context of the USB 3.0 standard, embodiments are not limitedthereto. It is contemplated that embodiments may be implemented in pastor future standards of USB, as well as other communication protocols andstandards including, but not limited to, active cable standards.

Generally speaking, due to the high data rates of USB 3.0 (e.g., 5Gb/s), the cable length of reasonably sized traditional passiveelectrical conductor cable assemblies is limited to about 3 meters orless due to skin and dielectric losses intrinsic to electricalconductors and dielectric materials. Further, conductor cables that arecompatible with USB 3.0 are very bulky and put stress on the smallconnectors that are used on laptops and consumer devices such ascamcorders. Because of these limitations, there may be interest in afiber optic cable for use with USB 3.0. A fiber optic cable may bedramatically thinner, more flexible, easier to carry for portable use,and may put much less stress on the connectors used in small, handhelddevices. Additionally, a fiber optic cable assembly may comprise cablelengths of 100 meter spans or more, allowing USB 3.0 to be used inmarkets such as video delivery and thin-client computing.

Referring now to FIG. 1, an embodiment of an active cable assembly 100is schematically depicted. The active cable assembly 100 generallycomprises a cable end 102, a communication circuit 120, an active codingcircuit 126, and a controller 130. The cable end 102 of the active cableassembly 100 is configured to mate with a corresponding cable end toform a data link suitable for communicating data. The cable end 102 cancomprise a connector having mechanical pins and alignment members suchas, for example, a receptacle, a plug, or the like. The cable end 102can comprise one or more cable end data lines 104 for communicativelycoupling with a corresponding cable end to transmit data signals. It isnoted that the term “signal,” as used herein can mean a waveform (e.g.,electrical, optical, magnetic, or electromagnetic), such as DC, AC,sinusoidal-wave, triangular-wave, square-wave, and the like. It isfurther more noted that the phrase “communicatively coupled,” as usedherein, can mean that components are capable of exchanging signals withone another such as, for example, electrical signals via a conductivemedium, electromagnetic signals via air, optical signals via opticalwaveguides, or the like.

In some embodiments, the one or more cable end data lines 104 cancomprise a first output data line 106 and a second output data line 108for communicating data signals from the communication circuit 120. Theone or more cable end data lines 104 can further comprise a first inputdata line 110 and a second input data line 112 for communicating datasignals to the communication circuit 120. Each of the first output dataline 106, the second output data line 108, the first input data line 110and the second input data line 112 can be electrically conductive or beformed from electrically conductive materials such as, for example,copper or the like. It is noted that the one or more cable end datalines 104 can include any number of data lines. Indeed, it iscontemplated that the embodiments described herein can be extended toinclude the number of data lines needed for compatibility with anydefined communication protocol.

The communication circuit 120 can be configured to communicatedc-balanced signals via the one or more cable end data lines 104 of thecable end 102. In some embodiments, the communication circuit 120 can beconfigured to communicate high speed data signals according to the USB3.0 standard. Accordingly, the communication circuit 120 can be operableto communicate about 5 Gigabit per second signals or greater, which canhave voltage swings of about +/−1 volt. The communication circuit 120can comprise a data transmitter 122 for transmitting data to the one ormore cable end data lines 104. The communication circuit 120 can furthercomprise a data receiver 124 for receiving data from the one or morecable end data lines 104 and communicating the received data to theactive coding circuit 126.

Referring still to FIG. 1, the active coding circuit 126 can beconfigured to process data signals prior to transmitting the datasignals through transmission data lines 128 to another cable end ordevice. In some embodiments, the active coding circuit 126 can comprisedrivers, equalizers and coding means to process a signal for longertransmission distances. Additionally, the active coding circuit 126 cancomprise drivers, equalizers and coding means to decode received signalsfor transmission via the one or more data lines according to a desiredcommunication protocol.

According to the embodiments described herein, the active coding circuit126 can be operable to process electrical signals into electricalsignals for extended transmission. For example, the active codingcircuit 126 can filter or amplify a received electrical signal.Alternatively or additionally, the active coding circuit 126 can beconfigured to transform electrical signals into optical signals, oroptical signals into electrical signals. Accordingly, the active codingcircuit 126 can comprise optical devices such as, for example, lasers,photodiodes, optical couplings, or the like. Moreover, it is noted thatthe transmission data lines 128 can comprise conductive data lines,optical data lines, or a combination thereof.

As is noted above, the active cable assembly 100 can comprise acontroller 130. The controller 130 can be operable to manage theexchange of data signals via the communication circuit 120 and theactive coding circuit 126. Specifically, the controller 130 can executemachine readable instructions to automatically operate the communicationcircuit 120 and the active coding circuit 126 to implement any of themethods described herein automatically. The controller 130 can comprisea processor, an integrated circuit, a microchip, or any other computingdevice capable of executing machine readable instructions. Memory forstoring machine readable instructions can be communicatively coupled tothe one or more processors. The memory can comprise EPROM, RAM, ROM, aflash memory, a hard drive, or any non-transitory device capable ofstoring machine readable instructions. The memory of the controller 130can comprise an algorithm written in any programming language of anygeneration (e.g., 1 GL, 2 GL, 3 GL, 4 GL, or 5 GL) such as, e.g.,machine language that may be directly executed by the processor, orassembly language, object-oriented programming (OOP), scriptinglanguages, microcode, etc., that may be compiled or assembled intomachine readable instructions and stored on a machine readable medium.

The controller 130 can be programmed to handle various maintenance andsetup functions for the communication circuit 120, the active codingcircuit 126, the controller 130, or combinations thereof. For example,the controller 130 can be configured to provide data accessible to thecontroller, such as, for example, diagnostic information, parametervalues, or the like. Moreover, the controller 130 can be commanded toperform certain functions or operate in various preprogrammed modes suchas, for example, debugging mode or the like. Additionally, thecontroller 130 can be reprogrammed to, for example, update the firmwareor to change operational parameters.

In some embodiments, the controller 130 can comprise communication pads132 that can exchange signals to perform any of the maintenance andsetup functions described herein. For example, the controller can becoupled to a printed circuit board and the communication pads 132 can beconductive pads fabricated on the printed circuit board. A communicationfixture can be communicatively coupled to the communication pads 132 viaspring-loaded “pogo” pins. Accordingly, the hardware programming portsof a processor of the controller 130 can be accessed and the memoryassociated with the controller can be accessed or rewritten. During themanufacturing process, the communication pads 132 can becomeinaccessible (e.g., covered by a housing). Accordingly, thecommunication pads 132 may be desirable for use when the circuit boardis exposed.

The controller 130 can comprise one or more configurable communicationports that can be configured as an output for transmitting data signalsfrom the controller 130 and as an input for inputting data signals tothe controller 130. The configurable communication ports can be operableto communicate controller data signals according to a processorcommunication protocol such as, for example, RS-232, Serial PeripheralInterface (SPI), Inter-Integrated Circuit (I²C), alternative serialcommunication standards, or any other suitable communication standard.In some embodiments, the controller 130 can comprise a firstconfigurable communication port 134 and a second configurablecommunication port 136. It is noted that, while the embodiments depictedin FIGS. 1-6 the controller comprises the first configurablecommunication port 134 and the second configurable communication port136, the embodiments of the controller 130 described herein can compriseonly one configurable communication port or more than two configurablecommunication ports if desired.

Referring collectively to FIGS. 1-2C, the controller 130 can executemachine readable instructions to cause each of the first configurablecommunication port 134 and the second configurable communication port136 to operate as an input, or an output. When operating as an input,the configurable communication port can have a relatively highcontroller input impedance such as, for example, greater than about 1mega-ohm in one embodiment, or greater than about 5 mega-ohm in anotherembodiment. Referring to FIG. 2A, each of the first configurablecommunication port 134 and the second configurable communication port136 can operate as an output. When operating as an output, theconfigurable communication port can have a relatively low controllerimpedance that is lower than the relatively high controller inputimpedance. Referring to FIG. 2B, each of the first configurablecommunication port 134 and the second configurable communication port136 can operate as an input. Referring to FIG. 2C, the firstconfigurable communication port 134 can operate as an input and thesecond configurable communication port 136 can operate as an output.Accordingly, the controller 130 can transmit and receive controller datasignals contemporaneously. In embodiments, with only one configurablecommunication port, the controller 130 can transmit and receivecontroller data signals over the one configurable communication port byalternating between the one configurable communication port input andoutput.

As is noted above, the embodiments described herein can be configured tocommunicate data signals according to the USB 3.0 standard. Referring toFIG. 3, the communication circuit 120 can be communicatively coupled tothe controller 130 and the active coding circuit 126. The controller 130can also be communicatively coupled to the active coding circuit 126,which can be communicatively coupled to the transmission data lines 128.The first output data line 106 can be electrically coupled in series toa transmit capacitor 150. The transmit capacitor 150 can also beelectrically coupled in series to the data transmitter 122. The secondoutput data line 108 can be electrically coupled in series to a transmitcapacitor 152. The transmit capacitor 152 can also be electricallycoupled in series to the data transmitter 122. It is noted that, thephrase “electrically coupled,” as used herein, can mean to provide aconductive medium between one object and another object for thetransmission of electrical signals via the conductive medium.

In addition to compliance with the desired communication standard, theembodiments described herein can comprise components configured toisolate the data receiver 124 from the controller data signals. Forexample, in one embodiment, the first input data line 110 can beelectrically coupled to an isolation capacitor 154. The isolationcapacitor 154 can be electrically coupled to the data receiver 124. Thesecond input data line 112 can be electrically coupled to an isolationcapacitor 158. The isolation capacitor 158 can be electrically coupledto the data receiver 124.

The active cable assembly 100 can comprise one or more controlcharacteristic circuits for communicating with the controller 130. Insome embodiments, the first input data line 110 can be electricallycoupled to a first control characteristic circuit 142. The first controlcharacteristic circuit 142 can be electrically coupled in series withthe first configurable communication port 134. The second input dataline 112 can be electrically coupled to a second control characteristiccircuit 140. The second control characteristic circuit 140 can beelectrically coupled in series with the second configurablecommunication port 136.

Referring still to FIG. 3, the active cable assembly 100 can beconnected to a host device 200 to communicate data signals. The hostdevice 200 generally comprises a cable end 202, a communication circuit220, and a controller 230 communicatively coupled to the communicationcircuit 220. The cable end 202 can comprise one or more cable end lines204 comprising a first output data line 206 and a second output dataline 208 for communicating data signals from the communication circuit220 and a first input data line 210 and a second input data line 212 forcommunicating data signals to the communication circuit 220.

The host device 200 can comprise a communication circuit 220 forcommunicating according to the communication protocol of the activecable assembly and a controller 230 communicatively coupled to thecommunication circuit 220. The communication circuit 220 can comprise adata receiver 224 and a data transmitter 222. The data receiver 224 canbe electrically coupled to the first input data line 210 and the secondinput data line 212. The data transmitter 222 can be electricallycoupled in series to a transmit capacitor 250. The transmit capacitor250 can also be electrically coupled in series to the first output dataline 206. The data transmitter 222 can be electrically coupled to inseries to a transmit capacitor 252. The transmit capacitor 252 can alsobe electrically coupled in series to the second output data line 208.

The cable end 202 of the host device 200 is configured to mate with thecable end 102 of the active cable assembly 100 to form a data link forcommunicating data between the host device 200 and the active cableassembly 100. Specifically, an electrical connection 160 can be formedby placing corresponding data lines of the one or more cable end lines204 of the host device 200 in electrical contact with the one or morecable end data lines 104 of the active cable assembly 100.

Referring now to FIG. 4, the active cable assembly 100 can operate in a“mission mode” as high speed data is received by the data receiver 124.During “mission mode,” the first configurable communication port 134 andthe second configurable communication port 136 can be configured asinputs. When configured as inputs, the first configurable communicationport 134 and the second configurable communication port 136 can have arelatively high controller input impedance to eliminate disturbance ofthe high speed data transmission. Each of the first controlcharacteristic circuit 142 and the second control characteristic circuit140 can have parasitic inductance and capacitance (e.g., due toconductive traces or wiring) that operate as a source of reflectionsthat can corrupt the high speed data signals. The parasitic capacitancecan be modeled as parasitic capacitor 168 electrically connected betweenground and the first control characteristic circuit 142 and parasiticcapacitor 168 electrically connected between ground and the secondcontrol characteristic circuit 140.

To mitigate signal degradation, the first control characteristic circuit142 can comprise an isolation resistor 146 electrically coupled to eachof the first input data line 110 and the first configurablecommunication port 134. Additionally, the second control characteristiccircuit 140 can comprise an isolation resistor 144 electrically coupledto each of the second input data line 112 and the second configurablecommunication port 136. The resistance of each of the isolation resistor146 and the isolation resistor 144 can be set at a value high enough toisolate the first configurable communication port 134 and the secondconfigurable communication port 136 from significantly disturbing thehigh speed data signals. In order to set the resistance of the isolationresistor 146, the impedance of the first control characteristic circuit142, the parasitic capacitor 168, and the input impedance of the firstconfigurable communication port 134 can be considered. Similarly, theimpedance of the second control characteristic circuit 140, theparasitic capacitor 166, and the input impedance of the secondconfigurable communication port 136 can be considered to set theresistance of the isolation resistor 144. In some embodiments, theresistance value of each of the isolation resistor 144 and the isolationresistor 146 can be greater than or equal to about 500 ohms, such as,for example, greater than or equal to about 1,000 ohms in anotherembodiment. Alternatively or additionally, the isolation resistor 146and the isolation resistor 144 can be physically laid out on the printedcircuit board very close to the first input data line 110 and the secondinput data line 112, respectively, to minimize any transmission linestubs or capacitance on the high-speed side of the resistor.

Referring now to FIG. 5, the active cable assembly 100 can operate in a“controller communication mode” while the configurable communicationports 134, 136 communicate controller data signals via the one or morecable end data lines 104. In some embodiments, the active cable assembly100 can be connected to a programming fixture 300 to communicatecontroller data signals. The programming fixture 300 can comprises oneor more data lines 302 for exchanging data with the controller 130 ofthe active cable assembly 100. In one embodiment, the one or more datalines 302 can comprise an input data line 304 and an output data line306. The programming fixture 300 can further comprise a data receiver322 for receiving controller data signals from the controller 130 and adata transmitter 324 for transmitting controller data signals to thecontroller 130. The data receiver 322 can be electrically coupled to afixture resistor 310, which is electrically coupled to the input dataline 304. The data transmitter 324 can be electrically coupled to afixture resistor 308, which is electrically coupled to the output dataline 306.

Referring collectively to FIGS. 5 and 6, an electrical connection 360can be formed by placing corresponding data lines of the one or moredata lines 302 of the programming fixture 300 in electrical contact withthe one or more cable end data lines 104 of the active cable assembly100. Specifically, the first input data line 110 can be configured toreceive controller data signals from the output data line 306. The inputdata line 304 can be configured to receive controller data from thesecond input data line 112. Accordingly, the first configurablecommunication port 134 can operate as an input for receiving controllerdata signals and the second configurable communication port 136 canoperate as an output for transmitting controller data signals from thecontroller 130.

While the active cable assembly 100 is operating in the “controllercommunication mode,” the communication circuit 120 can be isolated fromthe controller data signals. In some embodiments, the controller datasignals can be distinct from the high speed data signals. In oneembodiment, the controller data signals can have a lower frequency thanthe high speed data signals. Alternatively or additionally, thecontroller data signal can have a larger voltage swing than the highspeed data signal. Specifically, in embodiments where the controllerdata signal uses the RS-232 standard, programming pulses can be fromabout 3 volts to about 5 volts. In embodiments, where the high speeddata signal follows the USB 3.0 standard, the high speed data signal canhave be a DC-balanced data stream with voltage of range of about 5volts−0.55 volts to about 5 volts+about 0.25 volts.

In some embodiments, the first control characteristic circuit 142 andthe isolation capacitor 154 can cooperate to isolate the communicationcircuit 120 from controller data signals. As depicted in FIG. 6, theinput resistor 162 and input resistor 164 models the effect of the inputresistance of the data receiver 124. Accordingly, the isolationcapacitor 154 can be electrically coupled to ground by the inputresistor 162 of the data receiver 124. Accordingly, a single order highpass filter can be formed at the input resistor 162 (i.e., the datareceiver 124) and a single order low pass filter can be formed at thefirst configurable communication port 134. Alternatively oradditionally, a voltage dividing action can be achieved by the isolationresistor 146 and the input resistor 162 (i.e., the data receiver 124),i.e., the isolation resistor 146 can have larger resistance than theinput resistor 162 to reduce current input to the communication circuit120. Accordingly, the controller data signals can be attenuated both thehigh pass filtering of isolation capacitor 154 and the voltage dividingaction before the attenuated signal can reach the communication circuit120. Additionally, the data receiver 124 can include anti-static clampdiodes to protect sensitive input gates. Accordingly, even if theattenuated signal were to exceed the safe level, the clamp diodes couldprovide secondary protection as long as the peak current is limited tonon-damaging levels.

Referring collectively to FIGS. 5 and 6, it is noted that in someembodiments the input resistance of the data receiver 124 can beconsidered symmetric at each of the inputs. Accordingly, the arrangementdescribed immediately above can be applied to the second controlcharacteristic circuit 140 and the isolation capacitor 158 to isolatethe communication circuit 120 from controller data signals.

Referring collectively to FIGS. 4 and 6, each of the input resistor 162and input resistor 164 can have an effective input resistance of about50 ohms. Accordingly, the isolation resistors 146, 144 can be set toabout 1,000 ohm and the isolation capacitors 154, 158 can be set toabout 0.1 uF, to isolate the communication circuit 120 from a controllerdata signals limited to about 1K baud. Alternatively or additionally,the capacitance of the isolation capacitors 154, 158 can be greater thanthe transmit capacitors 250, 252. In further embodiments, the value ofthe isolation capacitors 154, 158 can be greater than or equal to aboutdouble the capacitance of the transmit capacitors 250, 252 such as, forexample, greater than or equal to about four times the capacitance ofthe transmit capacitors 250, 252 in still a further embodiment. In someembodiments, the transmit capacitors 250, 252 and the transmitcapacitors 150, 152 can have substantially similar values, the transmitcapacitors 250, 252 and the transmit capacitors 150, 152 can beconfigured to follow the same communication standard. For example, whenfollowing USB 3.0, each of the transmit capacitors 150, 152, 250, 252can have capacitances of about 200 pF to about 1,000 pF. Accordingly,the capacitance of the isolation capacitors 154, 158 can be greater thanthe transmit capacitors 150, 152. Moreover, the value of the isolationcapacitors 154, 158 can be greater than or equal to about double thecapacitance of the transmit capacitors 150, 152 such as, for example,greater than or equal to about four times the capacitance of thetransmit capacitors 150, 152 in still a further embodiment.

Referring collectively to FIGS. 2A to 2C, embodiments of the activecable assembly 100 can be configured to automatically transition betweenthe “mission mode” and the “controller communication mode.”Specifically, the memory of the controller 130 can comprise machinereadable instructions for implementing a boot loader, i.e., each timethe controller is booted or powered on from an unpowered state, the bootloader can be executed. In one embodiment, the boot loader can cause thecontroller 130 to search for the presence of the programming fixture 300(FIGS. 3 and 4). If programming fixture 300 is detected, then thecontroller 130 can enter “controller communication mode.” If programmingfixture 300 is not detected, then the controller 130 can enter “missionmode.”

Referring to FIG. 2A, the controller 130 can begin the boot loader bysetting the first configurable communication port 134 and the secondconfigurable communication port 136 to outputs. As outputs, the firstconfigurable communication port 134 and the second configurablecommunication port 136 can have a relatively low controller impedance.The controller 130 can then cause the first configurable communicationport 134 and the second configurable communication port 136 to activelydrive the first input data line 110 and the second input data line 112to an initial voltage for an initialization time period. In someembodiments, the initial voltage can be sufficiently low to dischargeany voltage on the isolation capacitor 154 and the isolation capacitor158 to about 0 volts within the initialization time period. For example,the initial voltage can be set to about 0 volts to achieve aninitialization time period of about 10 milliseconds. In someembodiments, the initial voltage and the initialization time period canbe set to discharge any possible voltage on transmit capacitor 250 andtransmit capacitor 252 (FIGS. 3 and 4). This may be required if thecontroller 130 has yet to determine if the active cable assembly 100 isconnected to the programming fixture 300 or the host device 200.Alternatively or additionally, the initialization voltage can be set toany voltage distinguishable from a charge voltage. Accordingly, theinitialization voltage can be about 0 volts, a negative voltage value,or a positive voltage value.

Referring now to FIG. 2B, the controller 130 can set the firstconfigurable communication port 134 and the second configurablecommunication port 136 to inputs. As inputs, the first configurablecommunication port 134 and the second configurable communication port136 can have a relatively high controller input impedance. Thecontroller 130 can wait for a predetermined time period. Thepredetermined time period should be long enough for the programmingfixture 300 (if present) to charge the first input data line 110, thesecond input data line 112, or both to the charge voltage. Additionally,the predetermined time period should be short enough such that theleakage of each of the isolation capacitor 154 and the isolationcapacitor 158 will not cause appreciable drift during the measurementtime. Both the discharge time period and the predetermined time periodshould be long enough to allow several time-constants to ensure properequilibration of the voltages, yet not too long to be subject to drift.

Referring now to FIG. 2C, after waiting the predetermined time period,the voltage of the first input data line 110, the second input data line112, or both can be sensed. The sensed voltage, which should be equal toabout the charge voltage (e.g., about 3 volts) when the programmingfixture 300 is present, can be compared to a communication voltagerange. If the sensed voltage is within the communication voltage rangethe controller 130 can consider the programming fixture 300 as present.In some embodiments, the communication voltage range can be set as arange of voltages greater than a threshold voltage (e.g., about 1.5volts). In further embodiments, the communication voltage range can beset as a range of voltages less than a threshold voltage. In stillfurther embodiments, the communication voltage range can be set as arange of voltages that overlaps a threshold voltage, i.e., the rangeextends from a minimum voltage less than the threshold voltage to amaximum voltage that is greater than the threshold voltage.

When the programming fixture 300 is determined as present, thecontroller can enter the “controller communication mode.” For example,the first configurable communication port 134 can be set to an input andthe second configurable communication port 136 can be set to an output.As is noted above, when in “controller communication mode” thecontroller 130 can be reprogrammed or enter into a debugging mode, i.e.,the current firmware can be tested systematically while the controller130 provide parameter details. For example, the controller 130 canprovide internal information of the active coding circuit such as, forexample, a set of data indicative of the health of the laser, thephotodiode, and the integrity and loss of all the optical couplings.Alternatively or additionally, the controller 130 can be directed toperform diagnostic actions such as, for example, a sweep of laser drivesettings and detection of the photo current at the associated receiver.

Referring again to FIG. 2B, if the sensed voltage is not within than thecommunication voltage range, the controller 130 can consider theprogramming fixture 300 as absent. Accordingly, the controller can enterthe “mission mode” and the controller 130 can isolate the communicationcircuit 120 from the first configurable communication port 134 and thesecond configurable communication port 136. For example, the firstconfigurable communication port 134 and the second configurablecommunication port 136 can be set to inputs.

It should now be understood that embodiments described herein aredirected to apparatuses and methods for communication with amicroprocessor of an active cable assembly after the microprocessor hasbeen sealed within a cable housing. Specifically, the high-speedAC-coupled data lines can cooperate with the resistors and capacitors,described herein, to form a resistive bias tee communication circuit.Accordingly, modification of the firmware of the active cable assemblycan be performed post-manufacturing. Such external programming canreduce product returns and improve manufacturing yields.

The boot loading techniques described herein enable the multi-purposingof the high speed conductors of cables designed to be compliant withstandards that do not contemplate active cable implementations.Accordingly, the advantages of a microprocessor communication channelcan be applied to high-volume consumer cables that otherwise would notsupport firmware upgrades. Moreover, differences between the prototypedevelopment stage, where development is typically done onlarge-form-factor evaluation boards with non-destructive access tohardware programming ports, and the final product can be evaluated andquantified. A further advantage is that properties of the final productcable, which cannot otherwise be determined, can be evaluated andquantified. This information can be fed back into the design phase toimprove yield.

It is noted that terms like “typically,” when utilized herein, are notintended to limit the scope of the claims or to imply that certainfeatures are critical, essential, or even important to the structure orfunction of the embodiment. Rather, these terms are merely intended tohighlight alternative or additional features that may or may not beutilized in a particular embodiment of the disclosure.

For the purposes of describing and defining the concepts it is notedthat the terms “approximately” and “about” are utilized herein torepresent the inherent degree of uncertainty that may be attributed toany quantitative comparison, value, measurement, or otherrepresentation.

What is claimed is:
 1. An active cable assembly comprising: a cable endcomprising a conductive input data line; a data receiver electricallycoupled to the conductive input data line, wherein the data receiver isoperable to receive a DC-balanced data signal; a controllercharacteristic circuit electrically coupled to the conductive input dataline; and a controller communicatively coupled to the data receiver, thecontroller comprising a configurable communication port electricallycoupled to the controller characteristic circuit, and memory for storinga boot loader, wherein the controller executes the boot loader to: setthe configurable communication port as an input for the controller datasignals, the input having a high controller input impedance; and set theconfigurable communication port as an output for controller datasignals, the output having a low controller impedance that is lower thanthe high controller input impedance.
 2. The active cable assembly asclaimed in claim 1, further comprising an isolation capacitorelectrically coupled to the controller characteristic circuit, theconductive input data line, and the data receiver, wherein the isolationcapacitor is in series with the data receiver and located between thedata receiver and the conductive input data line.
 3. The active cableassembly as claimed in claim 1, wherein the controller characteristiccircuit comprises an isolation resistance.
 4. The active cable assemblyas claimed in claim 1, wherein the controller executes the boot loaderto selectively operate in a control communication mode or a mission modebased at least in part upon a voltage level sensed by the configurablecommunication port.
 5. The active cable assembly as claimed in claim 4,wherein the configurable communication port transmits the controllerdata signals to the conductive input data line, while the controlleroperates in the control communication mode.
 6. The active cable assemblyas claimed in claim 5, wherein the controller data signals correspond todiagnostic information, parameter values, or both.
 7. The active cableassembly as claimed in claim 4, wherein the controller operates in thecontrol communication mode when the voltage level is within acommunication voltage range.
 8. The active cable assembly as claimed inclaim 7, wherein the voltage level is sensed a predetermined time periodfrom setting of the configurable communication port as the input.
 9. Theactive cable assembly as claimed in claim 1, wherein the DC-balanceddata signal has a higher frequency than the controller data signals. 10.A method of communicating with a controller of an active cable assembly,the method comprising: setting a first configurable communication portand a second configurable communication port to outputs, wherein thefirst configurable communication port is communicatively coupled to afirst input data line and the second configurable communication port iscommunicatively coupled to a second input data line; driving the firstinput data line, with the first configurable communication port, and thesecond input data line, with the second configurable communication port,to 0 volts for a discharge time period; setting the first configurablecommunication port and the second configurable communication port toinputs; detecting, at the first configurable communication port, thesecond configurable communication port, or both, a voltage automaticallywith the controller; setting the first configurable communication portto an input, and the second configurable communication port to anoutput, when the voltage is greater than a threshold voltage; andcommunicating a controller data signal from the second configurablecommunication port to the second input data line.
 11. The method asclaimed in claim 10, further comprising: receiving a DC-balanced datasignal with the first input data line, with the first configurablecommunication port, and the second input data line.
 12. The method asclaimed in claim 10, further comprising: receiving an input controllerdata signal with the first input data line; and communicating the inputcontroller data signal from the first input data line to the firstconfigurable communication port.
 13. The method as claimed in claim 12,wherein the input controller data signal corresponds to program code,debugging code, or a combination thereof.
 14. The method as claimed inclaim 10, wherein the voltage is detected a predetermined time periodafter the first configurable communication port and the secondconfigurable communication port are set to inputs.
 15. The method asclaimed in claim 14, wherein the first configurable communication portand the second configurable communication port are set to inputs afterthe predetermined time period has elapsed.
 16. The method as claimed inclaim 10, wherein the controller data signal corresponds to diagnosticinformation, parameter values, or a combination thereof.
 17. The methodas claimed in claim 10, wherein the voltage is provided by a programmingfixture connected to the active cable assembly.
 18. An active cableassembly comprising: a cable end comprising a conductive input dataline; a data receiver electrically coupled to the conductive input dataline, wherein the data receiver is operable to receive a DC-balanceddata signal; a controller characteristic circuit electrically coupled tothe conductive input data line; and a controller communicatively coupledto the data receiver, the controller comprising a configurablecommunication port electrically coupled to the controller characteristiccircuit, and memory for storing a boot loader, wherein the controllerexecutes the boot loader to: set the configurable communication port asan output for controller data signals, the output having a lowcontroller impedance that is lower than the high controller inputimpedance; control the configurable communication port to drive theconductive input data line with an initial voltage; set the configurablecommunication port as an input for the controller data signals, theinput having a high controller input impedance; and control theconfigurable communication port to sense a voltage level on theconductive input data line after a predetermined period of time aftersetting the configurable communication port as an input.
 19. The activecable assembly as claimed in claim 18, further comprising an isolationcapacitor electrically coupled to the controller characteristic circuit,the conductive input data line, and the data receiver, wherein theisolation capacitor is in series with the data receiver and locatedbetween the data receiver and the conductive input data line.
 20. Theactive cable assembly as claimed in claim 18, wherein the controllercharacteristic circuit comprises an isolation resistance.
 21. The activecable assembly as claimed in claim 18, wherein the controller executesthe boot loader to selectively operate in a control communication modeor a mission mode based at least in part upon the voltage level sensedby the configurable communication port.
 22. The active cable assembly asclaimed in claim 21, wherein the configurable communication porttransmits the controller data signals to the conductive input data line,while the controller operates in the control communication mode.
 23. Theactive cable assembly as claimed in claim 21, wherein the controlleroperates in the control communication mode when the voltage level iswithin a communication voltage range.